Abstract: Water displacement curve is the most common method for water cut rule study, productive index prediction and recoverable reserve calibration. There are more than 50 methods of such a kind nowadays. However, selecting the curves that may describe the relationship between different water cut styles and recovery percent are the permanent topics to oilfield development operators. This paper presents the characteristic correlation between Zhong Dekang and Gao-I water displacement curves. The analysis shows that these two water displacement curves are of the characteristic of describing different water cut styles vs. recovery percent, the former has no corresponding water displacement curve, but the latter has. So the latter is the most perfect water displacement curve with wider application than the former.

Key words: water displacement curve, equation, correlation, comparison